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Sep 19, 2013
09/13

by
J. Caro; L. L. Salcedo

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The dynamics of systems composed of a classical sector plus a quantum sector is studied. We show that, even in the simplest cases, (i) the existence of a consistent canonical description for such mixed systems is incompatible with very basic requirements related to the time evolution of the two sectors when they are decoupled. (ii) The classical sector cannot inherit quantum fluctuations from the quantum sector. And, (iii) a coupling among the two sectors is incompatible with the requirement of...

Source: http://arxiv.org/abs/quant-ph/9812046v2

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Sep 24, 2013
09/13

by
V. I. Kozub; J. Caro

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We describe spin transfer in a ferromagnet/normal metal/ferromagnet spin-valve point contact. Spin is transferred from the spin-polarized device current to the magnetization of the free layer by the mechanism of incoherent magnon emission by electrons. Our approach is based on the rate equation for the magnon occupation, using Fermi's golden rule for magnon emission and absorption and the non-equilibrium electron distribution for a biased spin valve. The magnon emission reduces the...

Source: http://arxiv.org/abs/cond-mat/0412348v1

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Sep 19, 2013
09/13

by
J. Caro; C. Garcia-Recio; J. Nieves

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We fit the $^1 S_0 \Lambda\Lambda$ interaction in the nuclear medium to the masses of the experimentally known double-$\Lambda$ hypernuclei: $^{\phantom{6}6}_{\Lambda\Lambda}$He, $^{10}_{\Lambda\Lambda}$Be and $^{13}_{\Lambda\Lambda}$B. We derive this effective interaction from OBE J\"ulich $\Lambda\Lambda$-type potentials and using both Hartree-Fock and variational approaches. We find that the inclusion of $\Lambda\Lambda$ correlations in the variational scheme leads to significant...

Source: http://arxiv.org/abs/nucl-th/9801065v5

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28

Sep 19, 2013
09/13

by
José A. Díaz-García; Francisco J. Caro-Lopera

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The non isotropic noncentral elliptical shape distributions via pseudo-Wishart distribution are founded. This way, the classical shape theory is extended to non isotropic case and the normality assumption is replaced by assuming a elliptical distribution. In several cases, the new shape distributions are easily computable and then the inference procedure can be studied under exact densities. An application in Biology is studied under the classical gaussian approach and two non gaussian models.

Source: http://arxiv.org/abs/1009.3168v1

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Sep 22, 2013
09/13

by
Jose A. Diaz-Garcia; Francisco J. Caro-Lopera

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This work proposes a new model in the context of statistical theory of shape, based on the polar decomposition. The non isotropic noncentral elliptical shape distributions via polar decomposition is derived in the context of zonal polynomials, avoiding the invariant polynomials and the open problems for their computation. The new polar shape distributions are easily computable and then the inference procedure can be studied under exact densities. As an example of the technique, a classical...

Source: http://arxiv.org/abs/1004.0483v1

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Jun 28, 2018
06/18

by
José A. Díaz-García; Francisco J. Caro-Lopera

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Some ideas studied by Lele (1993), under a Gaussian perturbation model, are generalised in the setting of matrix multivariate elliptical distributions. In particular, several inaccuracies in the published statistical perturbation model are revised. In addition, a number of aspects about identifiability and estimability are also considered. Instead of using the Euclidean distance matrix for proposing consistent estimates, this paper determines exact formulae for the moments of matrix $\mathbf{B}...

Topics: Statistics, Statistics Theory, Mathematics

Source: http://arxiv.org/abs/1507.03315

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Sep 21, 2013
09/13

by
J. Caro; E. Ruiz Arriola; L. L. Salcedo

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The $\sigma$-$\omega$ model of nuclei is studied at leading order in the $1/N$ expansion thereby introducing the self consistent Hartree approximation, the Dirac sea corrections and the one fermion loop meson self energies in a unified way. For simplicity, the Dirac sea is further treated within a semiclassical expansion to all orders. The well-known Landau pole vacuum instability appearing in this kind of theories is removed by means of a scheme recently proposed in this context. The effect of...

Source: http://arxiv.org/abs/nucl-th/9609031v1

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Jun 30, 2018
06/18

by
Jose A. Diaz-Garcia; Francisco J. Caro-Lopera

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This paper proposes a generalisation of the Pearson type II distribution, which shall termed Pearson Type II-Riesz distribution, based in the Kotz-Riesz distribution. Specifically, the central nonsingular matricvariate generalised Pearson type II-Riesz distribution, beta-Riesz type I distributions and the joint density of the singular values for real normed division algebras are obtained.

Topics: Mathematics, Statistics Theory, Statistics

Source: http://arxiv.org/abs/1407.4551

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Sep 18, 2013
09/13

by
J. Caro; E. Ruiz Arriola; L. L. Salcedo

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Dirac sea corrections for bulk properties of finite nuclei are computed within a self-consistent scheme in the $\sigma$-$\omega$ model. The valence part is treated in the Hartree approximation whereas the sea contribution is evaluated semiclassically up to fourth order in $\hbar$. Numerically, we find a quick convergence of the semiclassical expansion; the fourth order contributing much less than one percent to the binding energy per nucleon.

Source: http://arxiv.org/abs/nucl-th/9601033v1

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Sep 21, 2013
09/13

by
J. Caro; C. García-Recio; J. M. Nieves

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The $\Lambda$-$\Lambda$ effective interaction, in the channel $L=S=0$, in the nuclear medium is fitted to the available binding energies, $B_{\Lambda\Lambda}$, of double $\Lambda$ hypernuclei: $^{6}_{\Lambda\Lambda}$He, $^{10}_{\Lambda\Lambda}$Be and $^{13}_{\Lambda\Lambda}$B. The mesonic decay of these hypernuclei is also investigated. Finally, this effective interaction is used to predict the binding energies and mesonic decays widths of heavier double $\Lambda$ hypernuclei.

Source: http://arxiv.org/abs/nucl-th/9711035v1

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Sep 19, 2013
09/13

by
J. Caro Ramon; N. Kaiser; S. Wetzel; W. Weise

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We extend our recent non-perturbative chiral SU(3) coupled channel approach to pion- and photon-induced $\eta$- and $K$-meson production off protons by including all strong and electromagnetic p-wave multipoles. We identify the p-wave amplitudes of the next-to-leading order SU(3) chiral meson-baryon Lagrangian with a coupled channel potential which is iterated to infinite orders in a separable Lippmann-Schwinger equation. Our approach to $\eta$- and $K$-photoproduction introduces no additional...

Source: http://arxiv.org/abs/nucl-th/9912053v1

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Sep 20, 2013
09/13

by
José A. Díaz-García; Francisco J. Caro-Lopera

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In this work is obtained an explicit form for the perturbation effect on the matrix of regression coefficients on the optimal solution in multiresponse surface methodology. Then, the sensitivity analysis of the optimal solution is studied and the critical point characterisation of the convex program, associated with the optimum of a multiresponse surface, is also analysed. Finally, the asymptotic normality of the optimal solution is derived by standard methods.

Source: http://arxiv.org/abs/1207.4391v1

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Sep 23, 2013
09/13

by
Jose A. Diaz-Garcia; Francisco J. Caro-Lopera

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This work sets the statistical affine shape theory in the context of real normed division algebras. The general densities apply for every field: real, complex, quaternion, octonion, and for any noncentral and non-isotropic elliptical distribution; then the separated published works about real and complex shape distributions can be obtained as corollaries by a suitable selection of the field parameter and univariate integrals involving the generator elliptical function. As a particular case, the...

Source: http://arxiv.org/abs/1012.5856v1

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Sep 18, 2013
09/13

by
Francisco J. Caro-Lopera; Jose A. Diaz-Garcia

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A case of the matrix Kummer relation of Herz (1955) based on the Pearson VII type matrix model is derived in this paper. As a consequence, the polynomial Pearson VII configuration density is obtained and this set the corresponding exact inference as a solvable aspect in shape theory.

Source: http://arxiv.org/abs/1201.5705v1

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Sep 22, 2013
09/13

by
J. Caro; E. Ruiz Arriola; L. L. Salcedo

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We present the first calculation of the $\hbar^4$-Wigner--Kirkwood corrections to a relativistic system of fermions in the presence of external scalar and vector potentials. The method we propose allows to compute efficiently semiclassical corrections to one body operators such as mean energies and local densities. It also preserves gauge invariance and produces explicitly convergent results despite some apparent divergencies at the classical turning points. As a byproduct we obtain the...

Source: http://arxiv.org/abs/nucl-th/9410025v1

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Sep 17, 2013
09/13

by
Jose A. Diaz-Garcia; Francisco J. Caro-Lopera

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This work finds the non isotropic noncentral elliptical shape distributions via SVD decomposition in the context of zonal polynomials, avoiding the invariant polynomials and the open problems for their computation. The new shape distributions are easily computable and then the inference procedure is based on exact densities instead of the published approximations and asymptotic densities of isotropic models. An application of the technique is illustrated with a classical landmark data in...

Source: http://arxiv.org/abs/1003.4780v1

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Jun 26, 2018
06/18

by
Francisco J. Caro-Lopera; José A. Díaz-García

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In this paper a new approach is derived in the context of shape theory. The implemented methodology is motivated in an open problem proposed in \citet{GM93} about the construction of certain shape density involving Euler hypergeometric functions of matrix arguments. The associated distribution is obtained by establishing a connection between the required shape invariants and a known result on canonical correlations available since 1963; as usual in statistical shape theory and the addressed...

Topics: Mathematics, Statistics Theory, Statistics

Source: http://arxiv.org/abs/1502.00738

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100

Sep 17, 2013
09/13

by
Jose A. Diaz-Garcia; Francisco J. Caro-Lopera

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This work sets the non isotropic noncentral elliptical shape distributions via QR decomposition in the context of zonal polynomials, avoiding the invariant polynomials and the open problems for their computation. The new shape distributions are easily computable and then the inference procedure can be studied under exact densities instead under the published approximations and asymptotic densities under isotropic models. An application in Biology is studied under the classical gaussian approach...

Source: http://arxiv.org/abs/1003.3439v1

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28

Sep 22, 2013
09/13

by
Jose A. Diaz-Garcia; Francisco J. Caro-Lopera

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The non isotropic and non central elliptical shape distributions via the Le and Kendall SVD decomposition approach are derived in this paper in the context of invariant polynomials and zonal polynomials. The so termed cone and disk densities here obtained generalise some results of the literature. Finally, some particular densities are applied in a classical data of Biology, and the inference is performed after choosing the best model by using a modified BIC criterion.

Source: http://arxiv.org/abs/1004.0242v1

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Sep 22, 2013
09/13

by
G. D. J. Smit; S. Rogge; J. Caro; T. M. Klapwijk

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We show that individual dopant atoms dominate the transport characteristics of nanometer sized devices, by investigating metal semiconductor diodes down to 15 nm diameter. Room temperature measurements reveal a strongly increasing scatter in the device-to-device conductance towards smaller device sizes. The low-temperature measurements exhibit pronounced features, caused by resonant tunneling through electronic states of individual dopant atoms. We demonstrate by a statistical analysis that...

Source: http://arxiv.org/abs/cond-mat/0309137v1

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Sep 22, 2013
09/13

by
G. D. J. Smit; S. Rogge; J. Caro; T. M. Klapwijk

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A boron impurity in silicon binding an extra hole is known to have only one bound state at an energy of just below 2 meV. The nature of the Si:B^+ ground state is however not well established. We qualitatively analyze the behavior in a magnetic field of isolated acceptors in a tetrahedral lattice binding two holes using group theory. Applying these results, we analyze recent measurements and conclude that the ground state of B^+ is most compatible with a non-degenerate Gamma_1 state.

Source: http://arxiv.org/abs/cond-mat/0309136v1

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Sep 22, 2013
09/13

by
G. D. J. Smit; S. Rogge; J. Caro; T. M. Klapwijk

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We have theoretically studied the effect of an electric field on the energy levels of shallow donors and acceptors in silicon. An analysis of the electric field dependence of the lowest energy states in donors and acceptors is presented, taking the bandstructure into account. A description as hydrogen-like impurities was used for accurate computation of energy levels and lifetimes up to large (several MV/m) electric fields. All results are discussed in connection with atomic scale electronics...

Source: http://arxiv.org/abs/cond-mat/0310492v1

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Sep 22, 2013
09/13

by
G. D. J. Smit; S. Rogge; J. Caro; T. M. Klapwijk

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Gate-induced wave function manipulation of a single dopant atom is a possible basis of atomic scale electronics. From this perspective, we analyzed the effect of a small nearby gate on a single dopant atom in a semiconductor up to field ionization. The dopant is modelled as a hydrogen-like impurity and the Schrodinger equation is solved by a variational method. We find that--depending on the separation of the dopant and the gate--the electron transfer is either gradual or abrupt, defining two...

Source: http://arxiv.org/abs/cond-mat/0309134v1

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Sep 22, 2013
09/13

by
J. Caro; I. D. Vink; G. D. J. Smit; S. Rogge; T. M. Klapwijk

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We observe a resonance in the conductance of silicon tunneling devices with a delta-doped barrier. The position of the resonance indicates that it arises from tunneling through the B^+ state of the boron atoms of the delta-layer. Since the emitter Fermi level in our devices is a field-independent reference energy, we are able to directly observe the diamagnetic shift of the B^+ level. This is contrary to the situation in magneto-optical spectroscopy, where the shift is absorbed in the measured...

Source: http://arxiv.org/abs/cond-mat/0309139v1

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Sep 22, 2013
09/13

by
H. Sellier; G. P. Lansbergen; J. Caro; N. Collaert; I. Ferain; M. Jurczak; S. Biesemans; S. Rogge

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We investigate by low-temperature transport experiments the sub-threshold behavior of triple-gate silicon field-effect transistors. These three-dimensional nano-scale devices consist of a lithographically defined silicon nanowire surrounded by a gate with an active region as small as a few tens of nanometers, down to 50x60x35 nm^3. Conductance versus gate voltage show Coulomb-blockade oscillations with a large charging energy due to the formation of a small potential well below the gate....

Source: http://arxiv.org/abs/cond-mat/0603430v2

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Sep 20, 2013
09/13

by
H. Sellier; G. P. Lansbergen; J. Caro; N. Collaert; I. Ferain; M. Jurczak; S. Biesemans; S. Rogge

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We report on spectroscopy of a single dopant atom in silicon by resonant tunneling between source and drain of a gated nanowire etched from silicon on insulator. The electronic states of this dopant isolated in the channel appear as resonances in the low temperature conductance at energies below the conduction band edge. We observe the two possible charge states successively occupied by spin-up and spin-down electrons under magnetic field. The first resonance is consistent with the binding...

Source: http://arxiv.org/abs/cond-mat/0608159v2